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All register 0x8, Why?

Mehmet TASPINAR
Intellectual 355 points
Other Parts Discussed in Thread: LMP91300

Hi,

I have used LMP91300, I write a  value in the register but, when I read this register to check it always returns 0x8.

Q1: Is that problem about short current?

Q2: how can I handle this problem?

Q3: Is there any default value to return fabrication condition?


Best regards,

Mehmet

  • 0
    TI__Genius 16890 points
    Hi Mehmet,

    Usually when the GUI returns 0x8 it means that there has been a problem reading the values from the LMP91300.

    The first step is to unplug the SWIF board from the computer and close the webench browser and the DOS command box. Plug the SWIF board back into the computer and start the software. Try reading a register.

    You should also have a LC tank connected to the board. It doesn't work when no LC tank is connected.

    You shouldn't try reading and writing when the switch is triggered and there is load current. This can drop the SWIF voltages at the pins of the LMP91300 and make the communication not work.

    Mike
  • 0 in reply to Michael Stout
    Intellectual 355 points
    Hi Mike,
    Thank you so much. I have fixed the problem. The sensor is now working correctly.

    But I have three problems;
    Q1:The sensor never start to create oscillation unless I connect oscilloscope or LCR bridge prope to CF capacitor pin. (CF value 47pF)
    Q2: I can not burn the the sensor. When I read status register (0x7e) it always return 0x20
    I would like to burn it from burn register (0x7F) as 0x20 (Burn all register)
    Q3: How can I use LUT table? I read TEMP64 register (0x79) as 0x65 and converted this value decimal and subtract 64. My value is 37 so where can I use this value in the LUT?

    Could you please help?
    Best regards,
    Mehmet
  • 0 in reply to Mehmet TASPINAR
    TI__Genius 16890 points
    Hi Mehmet,

    Could there be something wrong with how the Cf cap is mounted, so that when you touch the cap it connects it to the LMP91300?

    You would not be able to burn the registers if the oscillation is going.

    The use of the lookup table is described in section 8.2.3. It is used to modify the thresholds that are set in the part to work over temperature so that the switch distance stays the same over temperature. The LC tank will change value a lot over temperature.

    Mike
  • 0 in reply to Michael Stout
    Intellectual 355 points
    Hi Mike

    "You would not be able to burn the registers if the oscillation is going"
    you mean that I have to remove LC tank(coil) when I burn the LMP91300?
    Best regards,
    Mehmet
  • 0 in reply to Mehmet TASPINAR
    TI__Genius 16890 points

    Hi Mehmet,


    Sorry, it is a typo, it should be: You would not be able to burn the registers if the oscillation is NOT going.


    Mike